Wiktionary
mark down
vb. 1 To reduce the price of. 2 To write a memorandum about. 3 To subtract marks (points) for an error. 4 To write down.
WordNet
mark down
v. reduce the price of [ant: mark up]
Usage examples of "mark down".
The Peeps' higher base velocity would have made it easy to run Mark down if he'd tried to break in-system to join her.